A tooth is comprised of an inner dentin layer and an outer hard enamel that is coated with a protective layer called the acquired pellicle. The enamel layer is composed of hydroxyapatite crystals that create a somewhat porous surface. The pellicle or the enamel can become stained or discolored. It is believed that the porous nature of the enamel layer is what allows staining agents and discoloring substances to permeate the enamel and discolor the tooth.
Many substances that a person's teeth confront or come in contact with on a daily basis can “stain” or reduce the “whiteness” of one's teeth. In particular, food products, tobacco products and fluids such as tea and coffee that one consumes tend to stain one's teeth. These staining and discoloring substances can then permeate the enamel and cause noticeable discoloration of one's teeth. At the same time, some of the food and drinks can cause de-mineralization of the teeth.
One solution to the staining problem is through tooth bleaching. Some dentifrices, like toothpastes, gels, and powders, contain active oxygen or hydrogen peroxide liberating bleaching agents including peroxides, percarbonates and perborates of the alkali and alkaline earth metals or complex compounds containing hydrogen peroxide.
The amount of whitening obtained during tooth bleaching is dependent upon (1) the length of time each day the tray is worn; (2) the number of days the tray is worn; (3) the susceptibility of the teeth to the bleaching agent and (4) the concentration of active peroxides. For maximum whitening, an accelerated treatment time of approximately 18-20 hours per day is recommended.
One concern with some bleaching compositions is that prolonged treatment with highly concentrated bleaching agents present in the composition may contribute to tooth sensitivity following treatment. Even treatments with compositions not known to increase tooth sensitivity in most patients might still cause sensitivity in patients more prone to such sensitivity tendencies.
Another concern is that aggressive brushing, or any treatment with lower pH whitening compositions, as noted in Price et al. (The pH of Tooth-Whitening Products, J Can Dent Assoc, 66:421-6, 2000), may also lead to further de-mineralization of the tooth, decreasing its hardness.
Many attempts have been made to provide dentinal sensitivity relief, sometimes in a separate system from the bleaching system. Other attempts have been made to use a single system to attack both problems. At the same time, attempts have been made to re-mineralize the tooth, again in separate systems.
Therefore, there remains a need for a one-system approach to solving all the above mentioned problems and/or potential problems confronting the tooth.